International Research Journal of Agricultural Science and Soil Science (ISSN: 2251-0044) Vol. 5(5) pp. 129-136, August, 2015 Available online http://www.interesjournals.org/IRJAS DOI: http:/dx.doi.org/10.14303/irjas.2015.066 Copyright © 2015 International Research Journals

Full Length Research Paper

Effects of kola cultivation on soil fertility status of selected kolanut plantations in , Western

Adebowale L. A.1 and *Odesanya B. O.2

1Cocoa Research Institute of Nigeria, Ibadan (CRIN).Oyo state, 2Caleb University, Imota, State *Corresponding author’s email: [email protected]

Abstract

Kolanut is an economically important indigenous cash crop. Two species– cola nitida and cola acuminata are the most prevalent in Nigeria. Soils of five Kolanut plantations in different Local Government Areas (LGAs) in Ogun State were evaluated for effects of previous farming practices as well as their suitability for continuous use for kola cultivation. The sites were selected based on production outputs from the 10 Kolanut producing LGAs in the state. The stratified random technique at depths of 0-15cm, 15 – 30cm and 30 – 45cm was employed for soil sampling. Analytical results showed the pH of the soils to be between 5.29 and 7.57, sand content between 49.95% (Mamu) and 73.57% (Agoro) and clay contents between 17.57% (Odogbolu LGA) to 35.81% (Ijebu-North LGA). The silt contents ranged from 2.64%. (Ikenne LGA) and 14.72% (Ijebu North LGA). The predominant soil texture in these areas is sandy loamy. Soil organic carbon contents were adequate in all LGAs except Odogbolu LGA which was found to be below critical levels. Odogbolu LGA was also found to have Nitrogen (N) content below the critical level for the cultivation of kola. Available Phosphorus, P in the all five LGAs was between 8.03mg/kb and 13.98mg/kg which are above the critical required value of 3.7mg/kg soil. Exchangeable Potassium ranged from 0.08cmol/kg in Ikenne LGA to 0.44cmol/kg in LGA. The Magnesium, Mg contents of the soils in all five LGAs were found to be below the critical level. The results confirm the fact that Kola plantations thrive under different soil conditions in the state hence soil management practices have to be established specifically for each farm for maximum yields. There is no one-fits-all remedy for the farms. Coppicing of old and expired trees would also help in achieving better productivity.

Keywords: Ogun, Physico-chemical, Kola Plantation.

INTRODUCTION

Kolanut is one of the several tropical tree crops used in Hamza and Babatunde 2001). At present, the demand for local and international trade. There are over forty species Kolanut exceeds its production hence there is a need to of Kolanut. Seven have edible nuts but the two most increase its total plantation acreage and nut yield per common and useful fruit producing species in Nigeria are tree. This can be achieved through a detailed study of the cola nitida (Gbanja) and cola acuminata (Abata). The existing conditions of the farms. Kolanut was a major former is of more economic importance than the latter as export earner for Nigeria before dependence of the C. acuminata is mostly used for traditional practices economy shifted to oil and its derivatives (Akinbode, especially rituals and on social occasions in Nigeria. 1982). Kolanut production in Nigeria ranges from 85,000 Kolanut is also used in the production of pharmaceutical to 127,000 metric tonnes annually (Ologunagba, 2009) drugs, wines (Beattie, 1970, Ogutuga, 1975), beverages, representing around 70% of world production1 liquors and confectionaries because of its caffeine (Famuyiwa, 1987, Quarcoo, 1973). content. Kolanut pod husk is used for livestock feeds Ogun state produces the largest amount of Kolanut in (Egbe and Sobamiwa 1989) and has also been utilized the country devoting about 65,000 hectares of land and for the production of liquid soap (Yahaya et al., 2001) as producing 80,000 MT of the crop in 2010/2011 (National well as the production of snail feed (Yahaya et al., 2001, survey on Agricultural Exportable commodities,2013). 130 Int. Res. J. Agric. Sci. Soil Sci.

Figure 1: Map of Ogun State showing the selected LGAs for study (depicted by*)

The largest collection market within the state is located at assessment of soil fertility status of the plantations and Sagamu. Kolanut is produced in 10 out of the 20 LGAs in recommend efficient land use practices to ameliorate it. the state. This study was conducted by taking soil samples from 5 of these plantations from different zones based on the production output (figure 1). The production MATERIALS AND METHODS of Kolanut is influenced by soil fertility and the ability of any soil to replace nutrients absorbed by crops depend Ogun State has a humid, tropical climate with high rainfall mainly on the clay type, mineral composition of the fine and temperature. 5 LGAs were chosen for this study out fraction and soil fraction in toposequence. Aiboni and of the 10 LGAs producing kola economically in the state. Ogunkunle (1988) have shown that the presence of The kola farms were found to be between 45 and 70 weatherable minerals in the fine sand fraction within years old. The five plantations chosen are located at 200cm of the profile is one of the conditions for high Mamu (Ijebu-North Local Government Area (LGA)), fertility of tropical soils.Most of the Kolanut plantations in Agoro (Odogbolu LGA) - ( zone). Sapala Ogun state are old, inherited and run by farmers Makinde (Owode – Obafemi LGA) – (Egba/Yewa zone) generally within the age bracket of 50 – 70 years. The and Igbepa (Sagamu LGA) and Ikenne (Ikenne LGA)- farmers “mine” nutrients from the soil through kola pod (Remo zone) covering the three geo-political zones of the harvests yearly but hardly employ practices to ensure state. Soil samples were collected using the auger nutrient replacement through processes like fertilizer sampler at 0-15, 15-30, and 30-45cm depths respectively applications. Ipinmoroti et. al. (2000) have reported falling 10 meters apart from each plantation. Several samples kola yields due to old age and soil nutrient depletion. were collected and mixed for each soil depth level to This investigation sought to affirm this phenomenon obtain composite samples. 15 composite samples from and determine the effects of this continuous depletion of the each farm were used. The samples were air-dried soil mineral resources on kola production through an and passed through a 2mm mesh sieve before Adebowale and Odesanya 131

Table 1: Physical and chemical properities of soil at kola plantation in Agoro (Odogbolu Iga) SOIL DEPTH H Sand Clay Silt Textural pH Org Total Avail K Ca Mg Na Mn Fe AI EA ECEC Base S Class C N P saturation Cm % % % % % Mg/kg cmol/kg cmol/kg cmol/kg cmol/kg Mg/kg Mg/kg cmol/kg cmol/kg cmol/kg percentage A Sandy 0-15 78.24 13.76 8 Clay 4.95 1.08 0.09 10.49 0.09 1.05 0.05 0.25 72.6 17.18 0.31 0.05 1.49 96.64 Sandy 15-30 72.8 18.48 8.72 Clay 5.22 0.69 0.06 8.13 0.09 0.66 0.04 0.25 35 13.83 0.42 0.06 1.1 94.54 Sandy 30-45 68.8 20.48 10.72 Clay 5 0.65 0.06 11.03 0.09 0.65 0.05 0.32 30.3 11.38 0.31 0.06 1.17 94.87 Sandy Mean 73.28 17.57 9.15 Clay 5.06 0.81 0.07 9.88 0.09 0.79 0.05 0.27 75.97 14.13 0.35 0.06 1.25 95.35 B Sandy 0-15 80.24 16.64 3.12 Clay 5.07 0.92 0.08 9.1 0.3 2.17 1.01 0.28 32.8 13.7 0.39 0.04 3.8 94 Sandy 15-30 70.24 20.64 9.12 Clay 5.4 0.5 0.04 10.52 0.13 0.72 0.05 0.25 25.5 11.19 0.36 0.07 1.22 94.26 Sandy 30-45 70.24 21.76 8 Clay 4.82 0.43 0.06 9.07 0.08 0.74 0.05 0.2 33.7 12.53 0.13 0.06 1.13 94.69 Sandy Mean 73.57 19.68 6.75 Clay 5.9 0.62 0.06 9.53 0.17 1.21 0.37 0.24 30.67 12.43 0.29 0.06 2.05 94.31 C Uncultivated Area Sandy 0-15 78.8 13.2 8 Clay 5.58 1.30 0.12 21.97 0.11 1.97 0.05 0.35 74.2 12.97 0.81 0.04 2.52 98.41 Sandy 15-30 80.24 11.76 8 Clay 5.95 0.50 0.04 7.51 0.04 0.88 0.05 0.2 28.7 11.67 0.22 0.05 1.22 95.9 Sandy 30-45 70.8 22.48 6.72 Clay 5.97 0.36 0.03 17.46 0.11 1.26 0.05 0.35 19.9 11.33 0.3 0.05 1.82 97.25 Sandy Mean 76.61 15.81 7.57 Clay 5.83 0.7 0.06 13.98 0.09 1.37 0.05 0.3 40.93 11.99 0.44 0.05 1.85 97.19

mechanical and chemical analysis. The values exchangeable cations were extracted with neutral obtained by the summation method while percent obtained are average values. IN NH4OAC and K, Mg and Ca contents were base saturation was calculated as follows: The soil textural class was determined by the determined using atomic absorption spectro- hydrometer method (Bouyoucos, 1951) using photometry. The Walkley and Black method was Exchangeable Base x 100 hexametaphosphate as the dispersing agent. Soil used for the determination of carbon contents ECEC 1 pH was determined in soil/water ratio of 1:2.5 (Walkley and Black, 1934) while exchangeable using a glass electrode pH meter, total Nitrogen acidity was determined by extraction with 0.05 IN RESULTS AND DISCUSSION was determined by the kjeldahl method while KCl and titration with 0.05N NaOH using available P, was determined using the Bray No. 1 phenolphthalein as indicator (McClean, 1965). The results are presented in Tables 1 to 5. A and method (Bray and Kultz, 1945). The Effective cation exchange capacity (ECEC) was B are duplicates from composite soil samples 132 Int. Res. J. Agric. Sci. Soil Sci.

Table 2: Physical and chemical properities of soil at kola plantation in Mamu )Ijebu-North lga) Soil depth H Sand Clay Silt Textural pH Org Tota Avail K Ca Mg Na Mn Fe AI EA ECEC Base S Class C l P saturation N Mg/k cmol/k cmol/k cmol/k cmol/k Mg/k Mg/k cmol/k cmol/k cmol/k percentag % % % % % g g g g g g g g g g e A (cm) 22.4 Sandy 0-15 58.8 8 18.72 loamy 6.28 0.68 0.07 1.44 0.23 1.44 0.05 0.55 55.7 15.35 0.39 0.05 2.32 97.84 46.2 39.7 15-30 4 6 14 loamy Clay 5.61 0.44 0.04 9.32 0.13 0.97 0.05 0.3 18.2 11.16 0.36 0.66 1.51 96.03 30-45 44.8 45.2 10 loamy Clay 5.4 0.51 0.04 7.64 0.11 1.18 0.05 0.37 18.1 11.55 0.22 0.07 1.78 96.07 49.9 35.8 Mean 5 1 14.24 5.76 0.6 0.05 6.13 0.16 1.19 0.05 0.4 30.67 12.69 0.32 0.06 1.87 96.64 B (cm) 18.4 Sandy 0-15 66.8 8 14.72 Clay 5.45 1.29 0.11 7.45 0.15 1.65 0.05 0.37 50.3 17.83 0.32 0.06 2.28 97.37 30.4 Sandy 15-30 54.8 8 14.72 loamy 5.56 0.58 0.05 7.18 0.15 1.13 0.05 0.37 10.8 13.79 0.12 0.07 1.77 96.05 34.4 Sandy 30-45 50.8 8 14.72 loamy 4.92 0.51 0.04 6.15 0.15 0.96 0.05 0.37 4.6 12.33 0.11 0.07 1.6 97.63 57.4 27.8 Mean 7 1 14.72 5.31 0.79 0.07 6.93 0.15 1.25 0.05 0.37 21.9 14.64 0.18 0.07 1.88 96.35 C- Uncultivated Area (cm) Sandy 0-15 62.8 19.2 18 Clay 6.4 3 0.26 6.79 0.25 8.42 0.05 0.75 8.47 17.25 0.05 0.04 6.51 99.38 Sandy 15-30 56.8 25.2 18 loamy 5.78 1.65 0.14 7.53 0.44 4.32 0.05 0.72 6.63 16.31 0.13 0.03 5.56 99.46 34.8 Sandy 30-45 44.8 8 16.72 loamy 5.97 0.39 0.08 8.84 0.42 2.87 0.05 0.82 4.25 11.78 0.16 0.03 4.19 99.28 58.1 26.4 Mean 3 3 17.57 6.03 1.68 0.16 7.72 0.37 2.51 0.05 0.76 6.49 15.11 0.11 0.03 5.42 99.37

while U represents composite samples from soils where kola is cultivated are more acidic when a significant increase in Fe concentration in nearby not presently used for kola cultivation (control). compared to un-cultivated soils (control). There is cultivated soils compared to the uncultivated soil. also a decrease in available P, Ca, Na, AI and AGORO (ODOGBOLU LGA) base saturation percentage which might imply usage by kola trees for fruit production while there MAMU (IJEBU-NORTH LGA) The results are presented in Table 1. The textural is no significant difference in total N percent, K, class is predominantly sandy clay. The soils Mg and exchangeable acidity (EA). There is also Results obtained are presented in Table 2. Adebowale and Odesanya 133

Table 3: Physical and chemical properties soil at kola plantation in Sapala Makinde (Owode/Obafemi lga) Soil depth H Sand Clay Silt Textural pH Org Total Avail K Ca Mg Na Mn Fe AI EA ECEC Base S Class C N P saturation Cm % % % % % Mg/kg cmol/kg cmol/kg cmol/kg cmol/kg Mg/kg Mg/kg cmol/kg cmol/kg cmol/kg percentage A Sandy 0-15 54.8 30.48 14.72 loamy 5.4 1.15 0.1 9.86 0.21 1.61 0.05 0.35 102.9 19.02 0.12 0.05 2.22 97.75 Sandy 15-30 52.8 34.48 12.77 loamy 5.2 1.01 0.09 7.16 0.2 1.32 0.05 0.3 90.5 16.67 0.14 0.06 2.03 97.64 30-45 70.24 18.64 11.12 loamy Clay 5.18 0.94 0.08 11.06 0.19 1.43 0.05 0.4 83.3 16.61 0.33 0.05 2.14 97.66 Mean 59.28 27.87 12.87 5.26 1.03 0.09 10.03 0.2 1.46 0.05 0.35 92.23 17.43 0.2 0.65 2.13 97.48 B Sandy 0-15 64.24 21.26 14 loamy 5.37 1.59 0.34 11 0.36 2.38 0.05 0.3 98.2 18.11 0.48 0.05 2.94 98.3 Sandy 15-30 56.8 31.2 10 loamy 5.2 0.86 0.07 19.64 0.22 3.4 0.05 0.5 78.6 14.85 0.62 0.05 4.22 98.82 Sandy 30-45 52.24 42.66 5.12 loamy 5.03 0.72 0.06 11.93 0.09 1.47 0.05 0.2 66.9 14.88 0.51 0.05 1.86 97.31 Mean 57.76 32.53 9.71 5.2 1.06 0.09 13.88 0.16 1.42 0.05 0.33 81.23 15.95 0.53 0.05 3 98.14 C- Uncultivated Area Sandy 0-15 60.24 21.26 18 loamy 7.3 2 0.15 10.6 0.39 12.26 0.05 0.87 107.4 21.71 0.47 0.02 13.59 99.85 Sandy 15-30 58.24 29.76 12 loamy 7.4 1.01 0.09 8.51 0.22 4.44 0.05 0.57 69.4 20.8 0.49 0.02 5.28 99.62 Sandy 30-45 56.24 29.76 14 loamy 6.38 0.86 0.1 7.27 0.28 3.83 0.05 0.57 77.4 20.98 0.52 0.03 4.76 99.37 Mean 54.24 27.09 14.67 7.03 1.22 0.11 8.79 9.30 0.84 0.05 0.67 84.73 21.16 0.49 0.02 7.87 99.64

The soil textural class is mainly sandy loamy and SAPALA-MAKINDE (OWODE/OBAFEMI LGA) IGBEPA (SAGAMU LGA) loam clay There appears to be a depletion of the amount of organic carbon, available P, Ca Na, Fe The soil texturally is mainly sandy loamy. Soil textural class is sandy loamy. There is a and ECEC which could imply their consumption Cultivation of kola led to an increase in acidity decrease in organic carbon, total N percent, Ca, Fe, during the production of kola. However, there is (pH) and reduction in amounts of K, Ca, Na, Fe and ECEC indicating their being used up for kola also an increase in the amounts of Mn and AI and and ECEC. There are however, no significant production while there are increases in available P a negligible difference in the values for pH, total differences in organic carbon, total N, Mg, EA and and AI in soils that are being sued for kola N, K and EA when compared to virgin areas. The base saturation as well as an increase in available production. There are no appreciable differences results indicate minimal utilization of these the P. The results for this study are presented in in acidity, mg, Na, Mn, EA and base saturation essential minerals for growth of kola in Mamu. Table 3. percent. The results are as presented in Table 4. 134 Int. Res. J. Agric. Sci. Soil Sci.

Table 4: Physical and chemical properties soil at kola plantation in Igbepa (Sagamu Iga) Soil depth H Sand Clay Silt Textural pH Org Total Avail K Ca Mg Na Mn Fe AI EA ECEC Base S Class C N P saturation Cm % % % % % Mg/kg cmol/kg cmol/kg cmol/kg cmol/kg Mg/kg Mg/kg cmol/kg cmol/kg cmol/kg % A 0-15 67.55 19.2 13.28 Sandy Clay 6.43 2.48 0.22 7.88 0.5 7.03 0.05 1 94.5 19.35 0.5 0.04 5.62 99.54 15-30 67.55 31.2 12.8 Sandy Loamy 6.45 2.06 0.19 12.54 0.47 6.46 0.05 1.04 61.7 25.21 0.45 0.03 8.05 99.62 30-45 67.52 28.2 9.28 Sandy Loamy 6.88 1.59 0.14 10.92 0.39 7.91 0.05 0.55 55.6 25.67 0.48 0.04 8.9 99.55 Mean 67.54 24.53 11.79 6.59 2.04 0.18 10.58 0.44 7.13 0.05 0.86 70.6 23.33 0.48 0.04 8.52 99.57 B 0-15 69.52 23.24 7.28 Sandy Loamy 6.51 2.48 0.22 12.08 0.44 3.23 0.05 0.75 79.8 21.24 0.46 0.04 6.51 99.39 15-30 69.52 27.2 7028 Sandy Loamy 6.08 2.49 0.33 9.64 0.38 4.37 0.05 0.7 65.8 23.37 0.46 0.04 5.84 99.31 30-45 69.52 29.2 9.29 Sandy Loamy 6 2.06 0.19 10.74 0.37 4.53 0.05 0.62 33 25.55 0.37 0.04 5.61 99.29 Mean 61.52 26..55 6.61 6.2 2.34 0.21 10.92 0.4 4.81 0.05 0.69 59.4 23.53 0.43 0.04 5.99 99.33 C- Uncultivated Area 0-15 65.52 22.2 18.28 Sandy Loamy 6.56 3.72 0.41 11.09 0.24 9.93 0.05 0.57 91.7 23.64 0.36 0.04 10.51 99.62 15-30 53.52 39.2 19.28 Sandy Loamy 6.16 6.35 0.72 8.76 0.24 12.67 0.05 0.67 81.6 34.95 0.34 0.04 11.6 99.7 30-45 37.52 49.2 13.28 Sandy Clay 6 2.78 0.23 8.68 0.28 7.3 0.05 0.8 36.7 32.35 0.4 0.04 8.47 99.52 Mean 50.19 33.53 16.95 6.24 4.28 0.46 9.51 0.25 9.96 0.05 0.68 70 30.13 0.38 0.04 10.86 99.61

IKENNE (IKENNE LGA) from Ikenne (the most acidic location), Potassium in the affected plantations. All the soils studied (K), Calcium (Ca), Sodium (Na), Aluminum (Al), showed phosphorus levels above the critical value The soil textural class is sandy loamy from the Organic Carbon (Org. C), Phosphorus (P) and of 3.7 mg/kg even in cultivated areas. There is results as presented in Table 5. There is a Iron (Fe) are utilized for the growth of kola. The however, a reduction compared to the values decrease in available P and Fe indicating usage critical value for soil organic content is 1.05% and obtained in the adjacent forest implying its for kola production but no significant differences the values obtained for the entire plantation apart reduction for kola production. This can be on total N percent, K, Mg, Na, EA and base from Agoro are above the critical level. This can attributed to P-sorption in cultivated soils due to saturation percent compared with uncultivated be remedied by practices like surface mulching their clay contents. The soils therefore need to be areas. The soil at this location was found to be and/or application of organic fertilizers as monitored for nutrients to ensure the values do most acidic. required.The major source for soil organic carbon not fall below the critical levels required for kola It can be summarized from the findings that the is leaf litter mineralization. Total nitrogen, (N) production. The potassium contents of the soils in prevalent textural soil for kola plantation in Ogun percent has a critical value of 0.1% and all the Mamu, Sapara and Igbepa were found to be state is sandy loamy. It can also be seen that plantations have soils that have nitrogen contents above the critical value of 0.12cmol/kg both in cultivation of kolanut takes place in acidic soils above this value except for Agoro. However, most cultivated and uncultivated sections of the and leads to a further decrease in pH (increased of the soils apart from those of Igbepa and Ikenne plantations while the soils of Agoro and Ikenne acidity) with continuous cultivation although have values below the critical level post kola were found to have values below the critical value Ikenne could be considered an exception. The cultivation. There is thus a need to replenish the thus requiring fertilizer applications for efficient results indicate that for most plantations apart total N concentration between cycles of cultivation productivity. Adebowale and Odesanya 135

Table 5: Physical and chemical properties of soil at kola plantation in (Ikenne I.G.A.) SOIL DEPTH H Sand Clay Silt Textural pH Org Total Avail K Ca Mg Na Mn Fe AI EA ECEC Base S Class C N P saturation Cm % % % % % Mg/kg cmol/kg cmol/kg cmol/kg cmol/kg Mg/kg Mg/kg cmol/kg cmol/kg cmol/kg percentage A Sandy 0-15 69.52 22.2 8.28 Loamy 5.68 1.94 0.21 11.47 0.008 2.25 0.04 0.25 43.8 12.05 0.44 0.05 69.52 22.2 Sandy 15-30 57.52 33.2 9.28 Loamy 5.14 1.48 0.12 9.37 0.08 1.46 0.05 0.17 49.7 12.36 0.44 0.05 57.52 33.2 30-45 49.52 47.2 3.28 Sandy Clay 5 1.12 0.11 9.14 0.08 1.35 0.05 0.1 13.4 0.85 0.33 0.04 49.52 47.2 Mean 58.85 24.2 6.99 5.27 1.5 0.11 10.06 0.08 1.69 0.05 0.17 32.63 11.41 0.42 0.05 58.85 24.2 B Sandy 0-15 74.1 22.54 3.36 Loamy 5.73 2.32 0.18 8.2 0.09 1.84 0.05 0.3 76.2 9.44 0.42 0.04 74.1 22.54 Sandy 15-30 73.52 23.2 3.28 Loamy 5.51 1.35 0.14 10.43 0.07 2.04 0.05 0.17 65.5 12.54 0.37 0.04 73.52 23.2 Sandy 30-45 61.52 37.2 1.28 Loamy 5.38 1.38 0.11 8.15 0.08 1.78 0.05 0.17 14.9 11.38 0.32 0.04 61.52 37.2 Mean 69.71 27.63 2.64 5.55 1.62 0.15 8.93 0.08 2.22 0.05 0.21 52.37 11.12 0.37 0.04 69.71 27.63 C- Uncultivated Area Sandy 0-15 75.52 23.2 1.28 Loamy 5.54 1.56 0.14 8.07 0.08 1.43 0.05 0.25 59.3 12.99 0.44 0.03 75.52 23.2 Sandy 15-30 75.52 25.2 1.28 Loamy 4.97 1.43 0.15 8.02 0.09 1.21 0.05 0.15 49.5 9.95 0.3 0.04 75.52 25.2 Sandy 30-45 63.52 27.2 9.28 Loamy 5.37 1.22 0.11 15.14 0.09 1.39 0.05 0.15 35.5 12.47 0.32 0.04 63.52 27.2 Mean 70.19 25.2 4.61 5.29 1.4 0.13 10.47 0.09 1.48 0.05 0.18 48.1 11.83 0.35 0.04 70.19 25.2

The calcium contents of the soils in the five the kola plantation soils have average values of Kolanut production should commence immed- studied locations are above the critical level of 0.27cmol/kg, 0.24cmol/kg in sections A and B iately after the legumes or fallow period (National 0.1cmol/kg hence there would be no need to under kola plantation, the sodium content of the Open University of Nigeria: Principles of crop supplement this mineral.The magnesium contents uncultivated portion has a value of 0.30cmol/kg. rotation, 2013). This would help to avoid the major for the soils in all the plantations were below the This implied that there is not much depletion of Na disadvantages of monoculture farming prevalent critical value for growth of kola (0.08cmol/kg) due to cultivation of kola and might signify its non- in the plantations. This would also help to reduce except in Agoro where one of the cultivated essential nature for kola growth. This is consistent the build-up and effects of pests and diseases as portions had a value of 0.3cmol/kg. with the observation of Ayodele (1988) in kola the host would no longer be present all the time in This may be a direct consequence of the high production farms. The principles of crop rotation addition to reducing the depletion of available soil sand content of the studied soils. While sodium in would help in enhancing better yields of the crop. nutrients and destruction of soil structures. 136 Int. Res. J. Agric. Sci. Soil Sci.

Table 6: A summary of the effects of kola production on soils in the five locations are presented in

Location Textural class Acidity Minerals reduced Minerals with no Minerals Increased significant effect by kola cultivation Agoro Sandy Clay U=5. 83, A = 5.06, B= 5.09 P, Ca, Na, AI N, K, Mg Fe Mamu Sandy loamy/ U= 5.63, A= 5.76, B= 5.31 Org. C, P, Ca, Na, N, K Mn, AI loamy Clay Fe Sapala- Sandy loamy U=7.03, A= 5.26, B –=5.20 K, Ca, Na, Fe Org, C, N, Mg, P Makinde Igbepa Sandy loamy U=6.24, A= 6.59, B= 5/29 Org. C. N, Ca, Fe Mg, Na, Mn AI Ikenne Sandy loamy U= 5.5.29, A= 5/27, B=5.55 P, Fe N,Mg, Ba

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